This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-249676, filed Aug. 21, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an on-vehicle rod antenna device.
2. Description of the Related Art
FIG. 1A is a figure which shows an external configuration of the conventional on-vehicle rod antenna device. The rod antenna device 10 is constructed such that the antenna rod 13 is screwed and attached to the joint assembly 12 rotatably provided on the antenna base 11 mounted on the vehicle as shown in FIG. 1A.
FIG. 1B is a figure which shows an external configuration of the joint assembly 12, especially, in a state of detaching the antenna rod 13. In FIG. 1B, the antenna rod cover 13a forms the outer surface of the above-mentioned antenna rod 13.
A tip portion of the joint assembly 12 is covered with the antenna rod cover 13a by attaching the antenna rod 13. The plurality of hexahedron-shaped the projections 12b (for example, at 4 portions) made of the resin with the ABS resin etc. is radially formed, along outer circumferential surface of the metal cylindrical body 12a screwed at inner circumferential surface on an tip portion of the joint assembly 12. FIG. 1C shows an outline view of the joint assembly 12.
A size of the outside diameter at the end surface position of the outer circumferential surface of each the projections 12b is set slightly larger than a size of the inside diameter of this contact portion of the antenna rod cover 13a with the corresponding elasticity. When screwing and attaching the antenna rod 13 to mount it on the joint assembly 12, the inner surface of the antenna rod cover 13a is pushed by the projections 12b and transformed with elasticity. Thereby, the antenna rod 13 is prevented from loosening and departing from the joint assembly 12 by the outside power such as the vibrations.
That is, the projections 12b of the joint assembly 12 are formed as a stopper of the antenna rod 13 loosening to the vibration, etc. of the vehicle where the on-vehicle rod antenna device 10 is attached.
In the antenna rod 13 attached on the joint assembly 12, the installation metal fittings (not shown in the figure) with a tip portion which screws to the above-mentioned cylindrical body 12a in cylindrical bottom of the antenna rod cover 13a are laid underground. Then, the antenna rod element (not shown in the figure) is drawn out and undergrounded to the axis portion of the antenna rod cover 13a so as to be connected with this installation metal fittings.
The outside diameter at the outer circumferential surface position of the projections 12b of the joint assembly 12 is set larger than the inside diameter at the position where the antenna rod cover 13a of the corresponding antenna rod 13 corresponds as mentioned above. By screwing the installation metal fittings of the antenna rod 13 to the cylindrical body 12a of the joint assembly 12, when the antenna rod 13 is connected with the joint assembly 12, The projections 12b transform the antenna rod 13 by the elasticity of the antenna rod cover 13a and the frictional force corresponding to the elasticity power is given to the inner surface of the antenna rod cover 13a. As a result, the antenna rod 13 is prevented from loosening from the joint assembly 12 by the vibration of the vehicle etc.
Therefore, since the locking effect of the projections 12b of the joint assembly 12 changes greatly according to largeness of elasticity of antenna rod cover 13, largeness of friction with inside of the antenna rod cover 13, the outside diameter at the outer circumferential surface position and a size of the antenna rod cover 13a inside diameter. A very small allowance is required at the manufacturing, there is a disadvantage of raising the manufacturing cost as a result.
In addition, when the outer circumferential surface of the projections 12b wear out by repeating the attaching/detaching of the antenna rod 13 to the joint assembly 12, an initial locking effect is lost at once.
In EC safety standard (European safety standard), so that the projection object mounted on the car may never give the person harm, even the state of detaching the antenna rod 13, it is a reference that all positions where the human body may be contacted to the joint assembly 12 have the roundness of R 2.5 mm or more (5 mm or more in the diameter) and the small R and the corner of less than R 2.5 mm are prohibited.
However, the cylindrical body 12a and the projections 12b of the joint assembly 12 and the neighborhood thereof have small R and the corner of less than R 2.5 mm as seen from FIG. 1C. Therefore, it is not possible to agree with the above-mentioned EC safety standard.
An object of the present invention is to provide an on-board rod antenna device in which a sufficient locking effect can be maintained for a long period without requiring a sever size accuracy in manufacturing, and a pointed component is not exposed to an outside, where the human body may be contacted, even in a state of detaching the antenna rod.
An on-vehicle rod antenna device according to the present invention is characterized by comprising: an antenna rod; and an antenna base comprising a joint section to which the antenna rod is connected, in which the joint section comprises a tip portion, the tip portion is covered with the antenna rod in a state of connecting the antenna rod, and a substantially hemisphere recess or salient engaging with an inner circumferential surface of the antenna rod is formed on an outer circumferential surface of the tip portion.